Integrated pressure compensated load sensing system

ABSTRACT

An integrated pressure compensated load sensing system for a hydraulically actuated fork lift truck or the like having a lift cylinder, a tilt cylinder, and one or more auxiliary cylinders, said system including pump means which provides fluid pressure for acutating the respective cylinders via a directional control valve assembly including directional control valve members for controlling the direction and speed of actuation of the respective cylinders, and pressure compensating members associated with the respective directional control valve members and operative to maintain the selected speeds of actuation of the respective cylinders irrespective of variation of cylinder load. The system herein is further characterized in that when the pump means is a fixed displacement pump the valve assembly is provided with an unloading valve means operative to bypass excess pump flow to the tank thus to maintain the selected flow demand set by any directional control valve member or members. A yet further characterizing feature of the present system is that the valve assembly aforesaid with a minor modification in the unloading valve means section thereof may be adapted for use with a variable displacement pump controller means to set the variable displacement pump to meet the flow demand set by any one or more of the directional control valve members.

United States Patent Paul [ 1 Feb. 18, 1975 INTEGRATED PRESSURE COMPENSATED LOAD SENSING SYSTEM [75] Inventor: John C. Paul, Richmond Heights,

Ohio

[73] Assignee: Parker-Hannifin Corporation,

Cleveland, Ohio [22] Filed: Sept. 6, 1973 [21] Appl. No.: 394,560

[52] U.S. Cl 60/427, 60/445, 60/452, 60/484 [51] 1nt.Cl. Fl5b 11/16 [58] Field of Search 60/329, 420, 445, 452, 60/484. 427

[56] References Cited UNITED STATES PATENTS 2,238,060 4/1961 Kendrick 60/452 3,366,064 1/1968 Stephens ct al 60/452 3,444,689 5/1969 Budzich l t 60/427 3,470,694 10/1969 Budzich 60/427 [57] ABSTRACT An integrated pressure compensated load sensing sys- TANK tem for a hydraulically actuated fork lift truck or the like having a lift-cylinder, a tilt cylinder, and one or more auxiliary cylinders, said system including pump means which provides fluid pressure for acutating the respective cylinders via a directional control valve assembly including directional control valve members for controlling the direction and speed of actuation of the respective cylinders, and pressure compensating members associated with the respective directional control valve members and operative to maintain the selected speeds of actuation of the respective cylin ders irrespective of variation of cylinder load. The system herein is further characterized in that when the pump means is a fixed displacement pump the valve assembly is provided with an unloading valve means operative to bypass excess pump flow to the tank thus to maintain the selected flow demand set by any directional control valve member or members.

A yet further characterizing feature of the present system is that the valve assembly aforesaid with a minor modification in the unloading valve means section thereof may be adapted for use with a variable displacement pump controller means to set the variable displacement pump to meet the flow demand set by any one or more of the directional control valve members.

81 Claims, 7 Drawing Figures LO'S PATENTEB I 8W5 3,866,419

SHEEI 2 BF 5 9 LO-S INTEGRATED PRESSURE COMPENSATED LOAD SENSING SYSTEM SUMMARY OF THE INVENTION It is a principal object of this invention to provide an integrated pressure compensated load sensing system which includes a directional control valve assembly operatively interposed between a pump means and a plurality of actuating cylinders such as the lift and tilt cylinders of a fork lift truck, said valve assembly having one or more add-on directional control valves for auxiliary cylinders and said valve assembly having therein pressure compensating members for the respective directional control valve members, check valves, a relief valve, an unloading valve for use with a fixed displacement pump means, and, in the case of a variable displacement pump means, an unloading valve plug means whereby the self-contained valve assembly may readily be operatively connected in the system by conduit means leading to the pump means, to a tank, and to the respective actuating cylinders,

It is another object of this invention to provide a system in which the speed of actuation of a plurality of cylinders is determined by variable area orifices which are set by the extent of actuation of the respective directional control valve members to operating positions, the flow demands being maintained by the respective pressure compensator members and, when two or more directional control valve members are moved to operating position, check valves in the valve assembly downstream of the respective variable area orifices isolate the cylinder having the greatest load pressure from the cylinders having lower load pressures and, in that case, the respective pressure compensators automatically provide additional variable restriction thus to maintain the selected flow demand set by the respective directional control valve members.

It is another object of this invention to provide a system providing a novel arrangement in which different relief pressures obtain according to which of a plurality of cylinders is actuated either by itself or simultaneously with another or other cylinders.

Other objects and advantages will appear from the ensuing description.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic piping diagram of the system herein in association with the lift and tilt cylinders of a fork lift truck, the valve assembly being shown in elevatlon;

FIGS. 2-5 are cross-section views taken substantially along the lines 2--2 to -5, FIG. 1;

FIG. 6 is a fragmentary cross-section view similar to FIG. 2 showing the modified unloading valve section in association with the main and auxiliary pump controllers for a variable displacement pump; and

FIG. 7 is a cross-section view of a relief valve which provides a lower relief pressure when a particular directional control valve is actuated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The integrated pressure compensated load sensing system 1 herein is illustrated by way of example only in association with a fork lift truck 2 having a lift cylinder 3 for raising and lowering the fork 4 along the mast 5,

and a tilt cylinder 6 for tilting the mast 5 forward or backward about the pivot 7. The valve assembly 8 for controlling the speed and direction of actuation of the lift and tilt cylinders 3 and 6 comprises a main valve housing 9 having motor ports 10 and ll;ll connected to the respective cylinders 3 and 6 as shown, a pressure inlet port 12 connected by conduit 14 to the output port ofa pump 15, and a return port 16 connected by conduit 17 to the tank 18. As hereinafter explained in detail, the main valve housing 9 has therein lift and tilt spools I9 and 20 and associated pressure compensator spools 21 and 23.

If the equipment 2 has no other cylinders, a plate member 24 is secured by the screws 25 to the upper side of the main valve housing 9 but, if one or more auxiliary cylinders are provided, a corresponding number of auxiliary valve housings 26 are clamped to the main valve housing by said plate and screws 24 and 25, each auxiliary valve housing 26 having therein a valve spool 27 and associated pressure compensator spool 28 as hereinafter explained in detail.

The main valve housing 9 has therein the main pressure relief valve 29 and, in the case of a fixed displacement pump 15, the main valve housing 9 also has therein an unloading valve 30 which bypasses the pump 15 output to the tank 18 when all of the valve spools 19, 20, and 27 are in neutral inactive position and which bypasses excess flow when the pump 15 output exceeds the flow demand or demands set by operation of any one or more of the valve spools I9, 20, and 27 to operating position.

Each valve spool 19, 20 and 27 is preferably of the type which establishes a variable area orifice of flow capacity dependent upon the extent of movement thereof to an operating position to conduct fluid under pressure to actuate the associated cylinder, the pressure drop across such variable area orifice being sensed either by an unloading valve 30 in the case of a fixed displacement pump 15 or by a pump controller 31 in the case of a variable displacement pump 32 (see FIG. 6) thus to maintain substantially constant the pressure drop across the variable area orifice thus to satisfy the flow demand set by any valve spool irrespective of the load on its cylinder. When two or more of the valve spools are shifted to operating position at the same time with different load pressures on the respective cylinders, the compensator spool or spools associated with the cylinder or cylinders having the lower load pressure or pressures are operative to pinch off or restrict pressure or return flow through the associated spool or spools thus to maintain the selected pressure drops across the variable area orifices. The compensator spools 21, 23, and 28 also have further functions as later explained.

THE MAIN RELIEF AND UNLOADING VALVES 29 AND 30 (FIG. 2)

As shown in FIG. 2, the main valve housing 9 has a bore 35 which intersects the return passage 16' and return passage branch 16' and the pressure inlet passage 12' and which contains a pilot operated main relief valve 29 which is operative in well known manner to relieve excess pressure in the inlet passage 12 to the return passage 16' whenever the magnitude of the inlet pressure in the passage 12' and in the chamber 36 is sufficient to unseat the spring biased pilot valve member 37 thus to create a pressure drop across the orifice 38 such that the predominant inlet passage 12 pressure moves the main relief valve member 39 against the spring 40 to open communication between the inlet and return passages 12' and 16 to the return port 16.

The main valve housing 9 has another bore 45 in which is disposed an unloading valve member 46 which is biased by spring 47 to the position shown and which senses in the chambers 48 and 49 at its opposite ends pressure in the inlet passage 12 hereinafter referred to as HI-S i.e., the pressure upstream of the variable area orifices of the directional control valve spools 19, 20, and 27, and the pressure downstream of the spool valve variable area orifices, hereinafter referred to as LO-S. The unloading valve member 46 also has a bleed orifice 50 communicating the LO-S chamber 49 with the return passage 16'. When all of the valve spools 19, 20, and 27 are in neutral position, the LO-S pressure is at a minimum and hence pump 15 pressure I-II-S acting on the left hand end of the unloading valve member 46 will shift the latter toward the right against the spring 47 to bypass the pump 15 output from the inlet passage 12' to the return passage 16' via the metering orifices defined as by the circumferentially spaced apart series of circular recesses 51 in said unloading valve member 46. When one or more of the valve spools 19, 20, and 27 are shifted to operating position there will be a pressure drop from I-II-S to LO-S across the variable area orifice or orifices of the valve spools which will act in the respective chambers 48 and 49 to effect movement of the unloading valve member 46. By way of illustrative example, the spring 47 balances the unloading valve member when I-II-S is 75 psi greater than LO-S. Excess flow of oil from the pump 15 will be bypassed to the return passage 16 and port 16 by way of the metering slots 51 thus to maintain the flow demand or demands set by the valve spool or spools when shifted to operating position. As explained later in connection with the respective valve spool constructions, the downstream sides of the variable area orifices defined thereby are connected to the LO-S passage by way of check valves so that when two or more spools are simultaneously actuated to operating position the demand of the cylinder having the greatest load pressure will have its LO-S pressure in the unloading valve chamber 49 thus to maintain the 75 psi differential between HI-S and LO-S.

THE LIFT AND COMPENSATOR SPOOLS 19 AND 21 (FIG. 3)

The lift spool 19 is herein shown as being of the three way type for controlling the actuation of the single acting lift cylinder 3 and obviously it may be of the four way type for controlling actuation of a double acting cylinder if it be desired to have power actuation in both directions.

The lift spool bore 55 is intersected axially therealong by a return passage branch 16", a return core 56 communicating with the lift port via the compensator spool bore 57, the return passage 16', a lift port feed core 58 communicating with the lift port 10 via compensator spool bore 57, a 10-8 core 59 communicating with the LO-S passage leading to the unloading valve 30 via the check valve 60, a HI-S pressure core, a HI-S signal passage 61 communicating with the compensator spool bore 57, and a return passage branch 16". The lift spool 19 has metering slots 62 which form a variable area orifice between the pressure core HI-S and the LO-S core 59 when the lift spool 19 is stroked toward the right and has metering slots 63 which form a variable area meter-out orifice between the return core 56 and the return passage 16 when the lift spool 19 is stroked to the left. I

The lift pressure compensator spool 21 forms chambers 64 and 65 with the main valve housing 9 and is normally held in the position shown in FIG. 3 by the springs 67 and 68.

When the lift spool 19 is partially stroked toward the right the pressure core I-Il-S is communicated with the HI-S signal passage 61 to conduct HI-S pressure to the righthand chamber 65 of the compensator spool 21 and the load pressure in lift port 10 is communicated with the lefthand chamber 64 via spool groove 69, orifices 70, and holes 71. If the load pressure in lift port 10 exceeds the inlet pressure I-II-S, the compensator spool 21 will move to the right to compress the spring 68 and hence the land 72 of the compensator spool 21 will function as a load check valve to prevent backward flow of fluid from the lift port 10 into the pressure feed core 58. When the I II-S pressure in the righthand chamber 65 exceeds the load pressure in the lefthand chamber 64, the compensator spool 21 will shift to the left by compression of the spring 67 to move the land 72 to open communication between the lift port feed core 58 and the lift passage 10' and port 10 for flow of fluid from the pressure core HI-S'to the lift port 10 via variable area orifice 62, LO-S core 59, compensator spool groove 73, and passage 10. Such shifting of the compensator spool 21 to the left may be arranged to occur when the pressure in the righthand chamber 65 is, say, 5-10 psi greater than the pressure in the lift port 10 and lefthand chamber 64. Upon such stroking of the lift spool 19, and movement of the compensator spool 21 as aforesaid, flow through the variable area orifices at 62 will increase until the pressure drop across the variable area orifice is equal to 75 psi as aforesaid. It can be seen that a shifting of the lift spool 19 to increase or decrease the area of the variable area orifice at 62 will increase or decrease the flow therethrough to maintain, say, a 75 psi pressure drop. This manner of operation will maintain the desired speed of actuation of the lift cylinder 3 when the lift spool 19 is the only spool being actuated or when the lift spool 19 has the highest load pressure at the time that another spool or spools 20 or 27 are simultaneously actuated to operating position.

When another spool 20 or 27 has a higher working pressure than the working pressure of the lift spool 19,

the flow through the variable area orifice 62 increases slightly until the pressure downstream of the variable area orifice 62 is about psi less than the pressure in the I-II-S pressure core. At this 125 psi pressure drop across the orifice 62, the compensator spool 21 moves toward the left to compress both springs 67 and 68 to pinch down the metering orifice defined by the metering slots 74 and the edge of the compensator bore 57 adjacent the lift port feed core 58 thus to create an additional pressure drop as required to balance the system while maintaining a 125 psi pressure drop at the meter-in variable area orifice 62. The LO-S signal from the other spool 20 or 27 which is at the higher working pressure locks out such LO-S from the lift spool 19 at the check valve 60 and continue to increase the pump flow (FIG. 6) or to load the unloading valve 30 until the variable area orifice of such other spool or 27 is satisfied.

To lower the load on the lift cylinder 3 the lift spool is stroked to the left to form a variable area meter-out orifice 63 and, when the pressure drop across such meter-out orifice 63 between the return core 56 and the return passage 16 reaches, say, psi, the compensator spool 21 moves to the right against spring 68 to pinch down the orifice at the metering slots 75 to create additional pressure drop as required to balance out the system while maintaining the pressure drop at 50 psi at the meter-out orifice 63. The lowering operation of the lift cylinder 3 is not affected by the operation of any of the other spools 20 or 27. The pressure upstream of variable area orifice 63 reaches chamber 64 via openings 71 and the pressure downstream of orifice 63 reaches chamber 65 via orifice 76, and feed core 58 which then is in communication with the return passage 16'.

A combination of orifice and openings 71 permits emergency lowering of load should the compensator spool 21 remain stuck in its rightward position closing the metering slots 75 due to spring failure, contamination, etc. Because the area of holes 71 is much larger than the area of orifice 70, pressure in chamber 64 is nearly equal to the pressure in core 56.

THE TILT AND COMPENSATOR SPOOLS 20 AND 23 (FIG. 4)

As shown in FIG. 4, the tilt spool bore is intersected by the I-II-S pressure core, by a pair of LO-S cores 81 straddling said pressure core III-S, by a pair of tilt port feed cores 11' straddling said LO-S cores 81, and by a pair of return passages 16 straddling said feed cores 11, said LO-S cores 81 being joined together and communicated with the LO-S passage via the check valve 82 thus to vent the LO-S cores 81 to the tank 18 through the LO-S bleed down orifice 50 in the unloading valve 30 thereby preventing pressure bleed from the HI-S pressure core into the tilt port feed cores 11'.

The tilt spool 20 has meter-in slots 83 which define with the bore 80 variable area orifices between the HI-S pressure core and either branch of the LO-S pressure core 81 and meterout slots 84 which define with the bore 80 variable area orifices between the respective feed cores 11 and return passages 16'.

The compensator spool bore 85 in addition to being intersected by the HI-S pressure core, the LO-S cores 81, and the feed cores 1] is intersected by passages 86 which communicate with the respective tilt ports 11 to permit return flow through either port 11 to bypass the load check valves 87 associated with the respective tilt port feed cores 11. The compensator spool 23 is held in the position shown in FIG. 4 by the springs 88 and 89 and forms the chambers 90 and 91 in the main housing 9.

When it is desired to conduct fluid under pressure to the right tilt port 11, the tilt spool 20 is stroked to the left to establish a variable area meter-in orifice at 83 between the HI-S pressure core and the left branch of the LO-S cores 81, the LO-S pressure being conducted to the LO-S signal passage via the check valve 82 and such LO-S pressure fluid passes to the right-hand feed core 11 from the right branch 81 via non-metering portions of slots 84 and past the right load check valve 87 to the right tilt port 11. When the pressure in chamber 91 via orifice 92 is, say, 75 psi greater than the tank pressure in chamber 90 via orifice 93 and-left core 11', the compensator spool 23 is shifted to the left against spring 88 to permit return flow through groove 94. Return flow from the tilt cylinder 6 then flows through the left tilt port 11 and left bypass passage 86 to the left feed core 11' via the left compensator spool groove 94 and, from the left feed core 11, the fluid flows through the left variable area meter-out orifice at 84 to the left return passage 16. Should there be an over center load at the left tilt port. the compensator spool 23 serves as a counter-balance valve with LO-S pressure in the chamber 91 via the compensator spool orifice 92 and pressure in the left feed core 11 is in the other chamber 90 via the orifice 93 in the compensator spool 23 to close off return flow until the pressure in the chamber 91 exceeds the pressure in the other chamber 90 and hence in the return passage via orifice in the compensator spool by say 75 psi. When that occurs, the compensator spool 23 moves to the left to meter-out the return flow from the left tilt port 11 via the left meter-out orifice 95 adjacent groove 94 and, therefore, the pressure in the chamber 91 is held at return passage 16' pressure plus 75 psi.

Should there be a resisting load on the right tilt port 11 instead of an over center load on the left tilt port 11, pressure in 91 continues to increase above the pressure in 90 to shift spool 23 to the left until the right holes 96 in the compensator spool 23 open into the I-II-S pres sure core saturating the small orifice 92 thus reflecting I-II-S in 91 instead of LO-S as previously described, and further shifting the spool 23 to the left until the left holes 96 in the compensator spool 23 open into the LO-S core 81 whereat the pressure in the chamber 90 is approximately equal to LO-S pressure instead of return passage 1] pressure and the small orifice 93 is saturated or nearly saturated. In this condition of operation, the I-II-S and LO-S pressures will operate the unloading valve 30 to maintain HI-S 75 psi greater than LO-S by controlling the flow through the meter-in variable area orifice at 83. When the left holes 96 just break into the LO-S core 81, the spring 88 balances the compensator spool at 100 psi. The left holes 96 open only enough to provide the required flow through the left holes 96 and the orifice 93 to the return passage 16, partially saturating the orifice 93 until the pressure in the chamber 90 is 100 psi less than in the Hl-S pressure core. At the balance position of the compensator spool 23 the left groove 95 is wide open.

When another spool 19 or 27 at higher working pressure is actuated at the same time that the tilt spool 20 is in operating position, the flow through the variable area meter-in orifice at 83 increases until LO-S pressure in psi less than HI-S pressure. At such 125 psi pressure drop, the compensator spool 23 moves left a further amount against the spring 88 and pinches down the return flow at the orifice 97 adjacent groove 94 to create an additional pressure drop to bring the system into balance while maintaining a 125 psi pressure drop at the meter-in orifice 83. The LO-S signal from said other spool 19 or 27 operating at higher working pressure locks out the tilt LO-S at check valve 82 and continues to increase the pump flow (FIG. 6) or to load the unloading valve 30 until the other spool 19 or 27 variable area orifice is satisfied as well as the tilt spool orifice 83. The compensator spool 23 is in balance against the spring 88 when the pressure in the chamber 90 is 125 psi less than in the chamber 91.

The tilt spool 20 and tilt compensator spool 23 are of symmetrical construction and it will be apparent that the operation will be the same when the tilt cylinder 6 is actuated in the opposite direction with fluid pressure conducted to the left tilt port 11 and with return flow conducted from the right tilt port 11 to the right return passage 16'.

THE AUXILIARY AND COMPENSATOR SPOOLS 27 AND 28 (FIG.

Each auxiliary valve housing 26 has ports 101 for connection with double acting auxiliary cylinders (not shown). The auxiliary housing 26 has a spool bore 102 intersected by a feed passage 103 straddled by the branches of the LO-S core 104 which via the check valve 105 is communicated with the LO-S signal passage leading to the unloading valve 30. The branches of LO-S core 104 are straddled by the motor passages 101 and, in turn, the motor passages 101 are straddled by the return passages 16.

The auxiliary housing 26 is also formed with a bore 106 for the compensator spool 28 which is intersected by HI-S pressure core, the feed passage 103, the LO-S core 104, and one motor passage 101'. In the neutral position of the auxiliary spool as shown in FIG. 5, the LO-S core 104 is vented to the return passage 16' via the orifice 113 to chamber 112, check valve 105, the LO-S signal passage, and the bleed down orifice 50 in the unloading valve 30 thereby to prevent bleed buildup in the LO-S core 104 from the l-II-S pressure core and the feed core 103.

When the auxiliary spool 27 is stroked to the right to establish a variable area orifice at the right tapered portion 107, the compensator spool 28 biased by spring 108 blocks backward flow at the land 109 and, hence, the compensator spool 28 serves as a load check if the HI-S pressure in chamber 110 (via orifice 111) is less than the load pressure in the left motor port 101 which is sensed in the chamber 112 via the compensator spool orifice 113. By way of example, when HI-S pressure in the I-II-S pressure core is say 25-50 psi greater than the pressure at the left motor port 101, the compensator spool 28 shifts toward the right against the spring 108 for flow of fluid from the HI-S pressure core to the left motor port 101 and, in that case, the pressure drop between HI-S and LO-S upstream and downstream of the metering orifice 107 increases until the pressure drop is 75 psi at which the flow is maintained and the system is brought into balance by the unloading valve 30 or the variable pump. The spring 108 balances a 75 psi pressure drop between chambers 110 and 112 at about the midpoint of its travel at which point the groove adjacent metering slots 114 is wide open.

When the system is in balance, the foregoing manner of operation applies when the auxiliary spool 27 alone is actuated or when the auxiliary spool 27 has the highest working pressure when other spools 19 and/or are simultaneously actuated. When another spool 19 or 20 has a higher working pressure than the auxiliary spool 27, the flow through the variable orifice 107 increases slightly until the pressure downstream of the variable area orifice 107 is about 125 psi less than the pressure in the feed passage 103. At this 125 psi pressure drop the compensator spool 28 moves further to the right against spring 108 to pinch down the metering slots 114 as necessary to maintain the pressure in the feed core 103 at 125 psi greater than the pressure in the 8 left motor port 101. In this way, the pressure drop across the variable area metering orifice 107 is maintained at 125 psi. The LO-S signal from the other spool or spools 19 and/or 20 locks out at the check valve 105 and continues to increase the load on the unloading valve or the variable pump until the variable area orifice or orifice are satisfied as well as that of the auxiliary spool 27.

When the auxiliary spool is stroked to the right, the return flow from the upper motor port 101 passes to the return passage 16' via the right motor passage 101. As apparent, the auxiliary spool 27 is of four-way type whereby stroking of the same to the left establishes the variable area orifice at the left tapered portion 107 with the upper motor port 101 being the pressure port and the left motor port being the return port; and the compensator spool 28 operates in the manner previously described.

Each auxiliary housing 26 includes a pressure limiting pilot section 115 so that when the pressure in the chamber 112 reaches a prescribed limit, the pilot operated valve 116 opens against spring 117 whereupon the compensator spool 28 shifts to the right an additional amount pinching down the flow passage at the metering slots 114. Therefore, the compensator spool 28 becomes a pilot operated pressure reducer to maintain working pressure at a desired level when system pressure rises above the limit when another spool 19 and/or 20 has a higher working pressure than the auxiliary spool 27.

In the case where the spool 27 alone is actuated, or when it has the highest working pressure when spool 19 and/or 20 are simultaneously actuated, the LO-S pressure from chamber 112 to the unloading valve 30 or to the variable pump is limited to the prescribed limit, thereby limiting system pressure at a desired level. The compensator spool 28 in this case remains at the open position.

PUMP CONTROLLER FOR VARIABLE DISPLACEMENT PUMP (FIG. 6)

By way of illustrative example, the variable displacement pump comprises a piston type pump 32 such as disclosed in Malott US. Pat. No. 3,726,093 having a swash plate 120 which is movable to different angles of inclination to vary the displacement of the pump 32, the screw 121 being an adjustable stop screw for determining the maximum pump flow. The pump delivery pressure enters the pump controller 31 at the port 122 and acts on the differential area of the control spool 123, the spring 124 being a horsepower compensating spring which loads the control spool 123 as the control piston 125 moves toward the right and reduces the length of the spring 124. The actuation of the main controller spool 123 shuts off the holes 151, while actuation of the auxiliary controller spool 127 shuts off the holes 149 thus providing for minimum control bleed off flow at reduced pump delivery flow positions of the swash plate 120. The controller 31 is in balance when, for example, the control pressure in chamber 129 is equal to one half the pump delivery pressure. The spring 130 exerts force at the zero swash plate position to balance 200 psi pump delivery pressure and provides for positive upstroke at pump 32 start up. The passage 131 shown is plugged if the I-I1-S signal is received in passage 133 externally from the I-II-S port of the main valve housing 9. The spring 132 is a constant pressure spring whose length is constant regardless of the swash plate 120 position and is used alone to provide a controller 31 that destrokes at a constant pressure setting and is used with the spring 124 to provide a horsepower compensated curve.

If the I-II-S signal is received internally from the pressure delivery passage 122 the passage 131 is open and passage 133 is plugged. The auxiliary control spool 127 receives 111-5 and LO-S signals to regulate the control pressure to maintain HI-S at 75 psi greater than LO-S.

The main valve housing 9 in this case has a plug 135 in the unloading valve bore 45 which provides a small orifice 136 to vent the LO-S signal area to the return passage 16' when all of the directional control valve spools 19, 20, and 27 are in neutral, the orifice 136 being saturated upon actuation of any valve spool. The reference numerals 137 and 138 denote holes which lead to the pump inlet area 139 to reduce the control pressure in the chamber 129 for I-II-S from the holes 140 and 128. The spring 141 balances the compensator spool 127 when pressure in the chamber 142 is 75 psi greater than in the LO-S chamber 143.

By way of review, the main controller 31 operates as follows with the swash plate 120 being actuated by the control piston 125 and, of course, with the hydraulic and spring loads on the pistons (not shown) of the pump 32 tending to rotate the swash plate 120 in a direction to decrease the pump output flow, this being resisted by control pressure in the chamber 129 behind the control piston 125. The pressure passage 122 supplies pump pressure internally to the controller 31 from the pump delivery port area and it feeds through a small orifice 144 to the control pressure area 129 with the controller 31 being in balance when the control pressure in chamber 129 is approximately one half of the delivery pressure in passage 122. The control pressure is regulated by the pressure working on the differential area ofthe control spool 123 to move it to the left against the springs 124 and/or 132 loading it. When the control spool 123 thus moves to the left it bleeds off the control pressure chamber 129 through the orifice 145 and on through the holes 173 to the inlet area 146. As already mentioned, the spring 132 is a constant pressure spring whose length remains constant regardless of the swash plate 120 position whereas the spring 124 is a horsepower compensating spring and its load on the spool 123 is increased as the control piston 125 moves in the decreased flow direction and reduces its length. The spring 132 is used alone to provide a controller 31 that destrokes at a constant pressure setting and is used in combination with the spring 124 to provide a horsepower compensated curve. Also as previously mentioned, the spring 130 with a force at zero swash plate position sufficient to balance a pump delivery pressure of say 200 psi provides for positive upstroke at pump 32 start up.

When a pump 32 of the character indicated and a main controller 31 are used in combination with a pressure compensated directional control valve assembly 8, the auxiliary control spool 127 provides a second parallel bleed-off path for the control pressure in chamber 129. As shown in FIG. 6 this auxiliary control spool receives two pressure signals HI-S and LO-S and responds to regulate the control pressure in chamber 129 and thereby to regulate the swash plate 120 position and pump 32 delivery flow to whatever amount is required to maintain the I-II-S signal at 75 psi above the LO-S signal. This is accomplished by bleed-off of the control pressure in chamber 129 through the orifice 147 and on through the holes 137 and 138 to the inlet area 139 thereby reducing control pressure. The HI-S signal can be supplied externally as shown in FIG. 6 from the directional control valve assembly 8 through the passage 133 in which case the passage 131 is plugged internally. Alternatively, the HI-S signal can be supplied internally through the passage 131 in which case external passage 133 is plugged off. The HI-S signal reflects through the holes 140 and 128 to the area 142 at the left end of the spool 127. The LO-S signal reflects through the hole 148 to the area 143 at the right end of the spool 127. The spring 141 balances the spool 127 when the pressure in chamber 142 is 75 psi greater than the pressure in chamber 143.

An additional set of feed holes 149 permit flow from the HI-S signal through the passage 150 and on through the holes 151 working in parallel with the orifice 144 in the main controller spool 123 to provide maximum recovery speed when both control spools 123 and 127 are in inactive position as shown. Actuation of the main controller spool 123 shuts off the holes 151 while actuation of the auxiliary controller spool 127 shuts off the holes 149 thus providing for minimum control bleed off flow at reduced pump delivery flow positions of the swash plate 120. There is no control bleed off flow at the full pump delivery flow position of the swash plate 120.

THE TILT RELIEF VALVE (FIG. 7)

The tilt relief valve 160 as shown in FIG. 7 limits the system pressure to a lower limit whenever the tilt pressure reaches a maximum. The LO-S signals from the auxiliary, lift, and tilt spools 27, 19, and 20 join downstream of the respective check valves 105, 60, and 82 where the highest LO-S pressure continues through the passages 161, 162, and 163 to the unloader 30 or pump 15, the orifice 164 being the LO-S bleed down orifice 50 (FIG. 2) or the orifice 136 (FIG. 6). The tilt LO-S signal passage upstream of its check valve 82 also flows to the chamber 165 and to the chamber 166 via the small orifice 167. If the pressure in the chamber 166 exceeds the preset limit of the spring biased pilot operated valve 168, the latter opens for pilot flow via the orifice 167 to the return passage 16' to decrease the pressure in chamber 166 relative to the pressure in chamber 165 whereupon the compensator spool 169 moves to the left against spring 170 to pinch down the LO-S flow at the orifice 171 to limit the pump 15 flow or the unloading valve 30 flow to the tilt pressure limit. Therefore, when the tilt spool 20 is not actuated, the system pressure can rise above the tilt maximum pressure to the limit established by the main pump controller 31 or the main relief valve 29.

Having thus described embodiments of the present invention it can be seen that the present invention provides for automatic speed regulation of any one or more of a plurality of directional control valve members by employment of respective compensating spools which have multiple functions as aforesaid and which create additional pressure drops to maintain predetermined flow and hence pressure drop across a variable area metering orifice defined by each valve spool according to the extent of movement thereof from neutral position toward an operating position.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An integrated pressure compensated load sensing system comprising pump means; at least two fluid motors; a directional control valve having inlet, motor, and return ports respectively in fluid communication with said pump means, said fluid motors, and a tank; valve members movable in said directional control valve to control actuation of the respective motors and to define variable area orifices in the flow path of pressure fluid to the respective motors of sizes according to the extent of movement of the respective valve members; sensing means responsive to the pressure drops across said variable area orifices operative in conjunction with said pump means to maintain predetermined pressure drops across said orifices thus to actuate said fluid motors at desired speeds according to the sizes of said variable area orifices; check valves downstream of the respective orifices to render said sensing means responsive to the flow demand set by the valve member associated with the fluid motor of higher load pressure in the event of simultaneous actuation of said valve members; and pressure compensating members associated with the respective valve members; each pressure compensating member, when associated with the fluid motor of lower load pressure, sensing the flow demand of the variable area orifice set by the associated valve member and being moved to provide an additional restriction in one of the supply and return paths of fluid in said directional control valve thus to maintain the flow demand set by the variable area orifice of the valve member associated with the fluid motor of lower load pressure.

2. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve downstream of the variable area orifice set by its associated valve member.

3. The system of claim 1 wherein one of said pressure compensating members, when moved as aforesaid, provides such additional restriction downstream of the variable area orifice set by its associated valve member.

4. The system of claim 1 wherein one of said valve members is of three way type defining another variable area orifice in the return path of flow from its associated single acting fluid motor; the associated pressure compensating member sensing the pressure drop across said another variable area orifice and being moved by increase of the latter above a predetermined value to provide additional restriction in the return flow path thus to maintain predetermined return flow as set by said another variable area orifice.

5. The system of claim 1 wherein one of said pressure compensating members is a spring biased spool-like member axially movable in a bore in said directional control valve and having a first land constituting a load check valve downstream of the variable area orifice set by its associated valve member, and having a second land provided with metering slots defining such additional restriction downstream of the variable area orifice set by its associated valve member.

6. The system of claim 1 wherein one of said pressure compensating members constitute a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths to and from the associated fluid motor.

7. The system of claim 6 wherein one of said pressure compensating members, when'moved as aforesaid, provides such additional restriction in the return flow path from its associated fluid motor.

8. The system of claim 1 wherein said directional control valve has a load check valve downstream ofone of said pressure compensating members.

9. The system of claim 1 wherein one of said pressure compensating members is a spring biased spool-like msmller ax movable in a bore in ais fiasst na control valve arid having a fi rsfTind constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths acting on opposite ends of said spool-like member, and having a second land provided with metering slots defining such additional restriction in said return path, the ends of said spool-like member then being subjected to fluid pressure upstream and downstream of the variable area orifice of its associated valve member.

10. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve upstream of the variable area orifice set by its associated valve member.

11. The system of claim 1 wherein one of said pres sure compensating members is a spring biased spoollike member which is axially movable in a bore in said directional control valve and which when moved as aforesaid, provides such additional restriction upstream of the variable area orifice of its associated valve member.

12. The system of claim 11 wherein said one pressure compensating member, when moved as aforesaid, has its opposite ends respectively exposed to pressures upstream and downstream of said variable area orifice.

13. The system of claim 12 wherein said directional control valve has a spring biased pilot relief valve member therein which is exposed to downstream pressure acting on one end of said spool-like member and which is opened when such downstream pressure exceeds a predetermined value whereby upstream pressure acting on the other end of said spool-like member moves the latter to restrict flow through said additional restriction to the variable area orifice of its associated valve member.

14. The system of claim 1 wherein said directional control valve has a pilot operated relief valve comprising a spring biased pilot relief member which is exposed to fluid pressure downstream of one variable area orifice and upstream of its associated check valve and which is opened upon such fluid pressure exceeding a predetermined value, and a spring biased main valve member which provides a flow path to said sensing means via said variable area orifices and check valves and which is fluid pressure actuated to restrict said flow path when said pilot relief valve member is opened.

15. The system of claim 14 wherein said main valve member is axially reciprocable in a bore in said directional control valve and has one end exposed to such fluid pressure and the other end exposed to such fluid pressure via orifice means; the opening of said pilot relief valve member effecting reduction of fluid pressure acting on said other end relative to fluid pressure acting on said one end whereby said main valve member is moved to restrict said flow path as aforesaid.

16. The system of claim 15 wherein said main valve member is a spool-like member having a groove providing said flow path and an adjacent land to restrict said flow path when said main valve member is moved by predominant fluid pressure acting on said one end.

17. The system of claim 1 wherein said sensing means comprises an unloading valve having a spring biased unloading valve member movable in a bore in said directional control valve; said unloading valve member having its opposite ends respectively exposed to fluid pressure upstream of said variable area orifices and downstream of said check valves and being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said pump means to said return port.

18. The system of claim 17 wherein said directional control valve has orifice means communicating said downstream pressure with said return port to retain said downstream pressure at low value when said valve members are in inactive position closing said variable area orifices; said orifice means being saturated upon actuation of either or both of said valve members to establish said variable area orifice or orifices for buildup of downstream pressure for control of said unloading valve member.

19. The system of claim 18 wherein said orifice means comprises a passage in said unloading valve member.

20. The system of claim 17 wherein said unloading valve member is a spool-like member having a groove and metering slots in the adjacent land for metering such excess flow.

21. The system of claim 1 wherein said pump means comprises a variable displacement pump; and wherein said sensing means comprises a pump output adjustment means responding to the pressure drop across said variable area orifices to adjust the output of said pump according to the flow demands set by said valve members.

22. The system of claim 21 wherein said pump output adjustment means comprises a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifices and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.

23. The system of claim 22 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage in said directional control valve.

24. The system of claim 22 wherein said upstream and downstream pressures are derived from respective passages in said directional control valve.

25. The system of claim 22 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.

26. The system of claim 22 wherein saidmain controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.

27. The system of claim 22 wherein said auxiliary controller at pressure differentials less than such predetermined value is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction.

28. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve downstream of the variable area orifice set by its associated valve member, and provides such additional restriction downstream of the variable area orifice set by its associated valve member; and wherein the other of said pressure compensating members constitutes a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths to and from the associated fluid motor, and provides such additional restriction in the return flow path from its associated fluid motor.

29. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve in series with the variable area orifice set by its associated valve member, and provides such additional restriction in series with the variable area orifice of its associated valve member.

30. The system of claim 29 wherein the other of said pressure compensating members provides such additional restriction in the return flow path from its associated fluid motor.

31. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve downstream of the variable area orifice set by its associated valve member; and wherein another one of said pressure compensating members constitutes a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths to and from the associated fluid motor.

32. The system of claim 1 wherein one of said pressure compensating members, when moved as aforesaid, provides such additional restriction downstream of the variable area orifice set by its associated valve member; and wherein another one of said pressure compensating members, when moved as aforesaid, provides such additional restriction in the return flow path from its associated fluid motor.

33. The system of claim 1 wherein one of said valve members is of three way type defining another variable area orifice in the return path of flow from its associated single acting fluid motor; the associated pressure compensating member sensing the pressure drop across said another variable area orifice and being moved by increase of the latter above a predetermined value to provide additional restriction in the return flow path thus to maintain predetermined return flow as set by said another variable area orifice; and wherein said directional control valve has a load check valve downstream of another one of said pressure compensating members.

34. The system of claim 1 wherein one of said pressure compensating members is a spring biased spoollike member axially movable in a bore in said directional control valve and having a first land constituting a load check valve downstream of the variable area orifice set by its associated valve member, and having a second land provided with metering slots defining such additional restriction downstream of the variable area orifice set by its associated valve member; and wherein another one of said pressure compensating members is a spring biased spool-like member axially movable in a bore in said directional control valve and having a first land constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths acting on opposite ends of said spool-like member, and having a second land provided with metering slots defining such additional restriction in said return path, the ends of said spool-like member then being subjected to fluid pressure upstream and downstream of the variable area orifice of its associated valve member.

35.'The system of claim 31 wherein yet another one of said pressure compensating members constitutes a load check valve upstream of the variable area orifice set by its associated valve member. I 36. The system of claim 34 wherein yet another one of said pressure compensating members is a spring biased spool-like member which is axially movable in a bore in said directional control valve and which when moved as aforesaid, provides such additional restriction upstream of the variable area orifice of its associated valve member.

37. The system of claim 36 wherein said yet another one pressure compensating member, when moved as aforesaid, has its opposite ends respectively exposed to pressures upstream and downstream of said variable area orifice.

38. The system of claim 37 wherein said directional control valve has a spring biased pilot relief valve member therein which is exposed to downstream pressure acting on one end of said spool-like member of said yet another pressure compensating member and which is opened when such downstream pressure exceeds a predetermined value whereby upstream pressure acting on the other end of said spool-like member moves the latter to restrict flow through said additional restriction to the variable area orifice of its associated valve member.

39. The system of claim 31 wherein said sensing means comprises an unloading valve having a spring biased unloading valve member movable in a bore in said directional control valve; said unloading valve member having its opposite ends respectively exposed to fluid pressure upstream of said variable area orifices and downstream of said check valves and being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess fiow from said pump means to said return port.

40. The system of claim 39 wherein said directional control valve has orifice means communicating said downstream pressure with said return port to retain said downstream pressure at low value when said valve members are in inactive position closing said variable area orifices; said orifice means being saturated upon actuation of either or both of said valve members to establish said variable area orifice or orifices for buildup of downstream pressure for control of said unloading valve member.

41. The system of claim 40 wherein said orifice 16 and metering slots in the adjacent land for metering such excess flow.

43. The system of claim 31 wherein said pump means comprises a variable displacement pump; and wherein said sensing means comprises a pump output adjustment means responding to the pressure drop across said variable area orifices to adjust the output of said pump according to the flow demands set by said valve members.

44. The system of claim 43 wherein said pump output adjustment means comprises a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifices and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.

45. The system of claim 44 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage in said directional control valve.

46. The system of claim 44 wherein said upstream and downstream pressures are derived from respective passages in said directional control valve.

47. The system of claim 44 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.

48. The system of claim 44 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.

49. The system of claim 44 wherein said auxiliary controller at pressure differentials less than such predetermined value is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction.

50. The system of claim 35 wherein said sensing means comprises an unloading valve having a spring biased unloading valve member movable in a bore in said directional control valve; said unloading valve member having its opposite ends respectively exposed to fluid pressure upstream of said variable area orifices and downstream of said check valves and being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said pump means to said return port.

51. The system of claim wherein said directional control valve has orifice means communicating said downstream pressure with said return port to retain said downstream pressure at low value when said valve members are in inactive position closing said variable area orifices; said orifice means being saturated upon actuation of either or both of said valve members to establish said variable area orifice or orifices for buildup of downstream pressure for control of said unloading valve member.

52. The system of claim 51 wherein said orifice means comprises a passage in said unloading valve member.

53. The system of claim 50 wherein said unloading valve member is a spool-like member having a groove and metering slots in the adjacent land for metering such excess flow.

54. The system of claim 35 wherein said pump means comprises a variable displacement pump; and wherein said sensing means comprises a pump output adjustment means responding to the pressure drop across said variable area orifices to adjust the output-of said pump according to the flow demands set by said valve members.

55. The system of claim 54 wherein said pump output adjustment means comprises a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifices and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.

56. The system of claim 55 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage in said directional control valve.

57. The system of claim 55 wherein said upstream and downstream pressures are derived from respective passages in said directional control valve.

58. The system of claim 55 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.

59. The system of claim 55 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.

60. The system of claim 55 wherein said auxiliary controller at pressure differentials less than such predetermined value is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction.

61. The system of claim 31 wherein said directional control valve has a pilot operated relief valve compris' ing a spring biased pilot relief member which is exposed to fluid pressure downstream of one variable area orifice and upstream of its associated check valve and which is opened upon such fluid pressure exceeding a predetermined value, and a spring biased main valve member which provides a flow path to said sensing means via said variable area orifices and check valves and which is fluid pressure actuated to restrict said flow path when said pilot relief valve member is opened.

62. The system of claim 61 wherein said main valve member is axially reciprocable in a bore in said directional control valve and has one end exposed to such fluid pressure and the other end exposed to such fluid pressure via orifice means; the opening of said pilot relief valve member effecting reduction of fluid pressure acting on said other end relative to fluid pressure acting on said one end whereby said main valve member is moved to restrict said flow path as aforesaid.

63. The system of claim 62 wherein said main valve member is a spool-like member having a groove providing said flow path and an adjacent land to restrict said flow path when said main valve member is moved by predominant fluid pressure acting on said one end.

64. The system of claim 35 wherein said directional control valve has a pilot operated relief valve comprising a spring biased pilot relief member which is exposed to fluid pressure downstream of one variable area orifice and upstream of its associated check valve and which is opened upon such fluid pressure exceeding a predetermined value, and a spring biased main valve member which provides a flow path to said sensing means via said variable area orifices and check valves and which is fluid pressure actuated to restrict said flow path when said pilot relief valve member is opened.

65. The system of claim 64 wherein said main valve member is axially reciprocable in a bore in said directional control valve and has one end exposed to such fluid pressure and the other end exposed to such fluid pressure via orifice means; the opening of said pilot relief valve member effecting reduction of fluid pressure acting on said other end relative to fluid pressure acting on said one end whereby said main valve member is moved to restrict said flow path as aforesaid.

66. The system of claim 65 wherein said main valve member is a spool-like member having a groove providing said flow path and an adjacent land to restrict said flow path when said main valve member is moved by predominant fluid pressure acting on said one end.

67. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve downstream of said variable area orifice; the movement of said compensating member providing such additional restriction downstream of said variable area orifice.

68. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve downstream of said variable area orifice; said valve member being of the three way type defining another variable area orifice in the return path of flow between said motor and return ports; said compensating member sensing the pressure drop across said another variable area orifice and being moved by increase of the latter above a predetermined value to provide additional restriction in the return flow path thus to maintain predetermined return flow as set by 1 said another variable area orifice.

69. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve downstream of said variable area orifice; said compensating member having a first land constituting said load check valve and a second land provided with metering slots defining such additional restriction downstream of the variable area orifice set by its associated valve member.

70. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid restriction in the return path of fluid flow to maintain the flow demand set by said variable area orifice; said compensating member constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths of fluid flow to and from a double acting fluid motor adapted to be connected to said motor ports; said housing having at least one load check valve downstream of said compensating member.

71. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively, a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid restriction in the return path of fluid flow to maintain the flow demand set by said variable area orifice; said compensating member constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths offluid flow to and from a double acting fluid motor adapted to be connected to said motor ports; said housing having load check valves in passages leading to said motor ports downstream of said compensating member; said housing also having bypass passages to bypass the respective load check valves for return fluid flow from the respective motor porst to said return port via said valve member.

72. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid restriction in the return path of fluid flow to maintain the flow demand set by said variable area orifice; said compensating member constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths of fluid flow to and from a double acting fluid motor adapted to be connected to said motor ports; said compensating member having a first land constituting said counter-balance valve which is opened by predetermined pressure differential in the supply and return paths acting on opposite ends of said compensating member, and having a second land provided with metering slots defining such additional restriction in said return path, the ends of said compensating member then being subject to fluid pressure upstream and downstream of said variable area orifice.

73. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motorm and return ports for connection with a fluid pressure source, a fluid motor and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve upstream of said variable area orifice; said compensating member providing such additional restriction upstream of said variable area orifice; and a spring biased pilot relief valve member in said housing exposed to downstream pressure acting on one end of said compensating member; said pilot relief valve member being opened when such downstream pressure exceeds a predetermined value whereby upstream pressure acting on the other end of said compensating member moves the latter to restrict flow through said additional restriction to said variable area orifice.

74. An unloading valve for an integrated pressure compensated load sensing system and the like comprising a housing having asupply passage for flow of pressure fluid from a pump to a fluid motor via a variable area orifice in a directional control valve and a return passage leading to a tank; a spring biased spool-like unloading valve member movable in a bore in said housing and having its opposite ends respectively exposed to fluid pressure upstream and downstream of such variable area orifice; said unloading valve member being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said supply passage to said return passage; and orifice means in said unloading valve communicating said downstream pressure with said return passage to retain said downstream pressure at low value when said variable area orifice is closed; said orifice means being saturated upon establishment of said variable area orifice for buildup of downstream pressure for control of said unloading valve member.

75. The unloading valve of claim 74 wherein said orifice means comprises a passage in said unloading valve member.

76. Output adjustment means for the variable displacement pump of an integrated pressure compensated load sensing system and the like, said output adjustment means responding to the pressure drop across a variable area orifice to adjust the output of said pump according to the flow demand set by said variable area orifice; said pump output adjustment means comprising a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in dis placement decreasing direction; amain spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifice and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.

77. The output adjustment means of claim 76 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage communicating with the dowstream side of said variable area orifice.

78. The output adjustment means of claim 76 wherein said upstream and downstream pressures are derived from respective passages communicating with the upstream and downstream sides of said variable area orifice.

79. The output adjustment means of claim 76 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.

80. The output adjustment means of claim 76 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the in take side of said pump.

81. The output adjustment means of claim 76 wherein said auxiliary controller, at pressure differentials less than such predetermined value, is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction. 

1. An integrated pressure compensated load sensing system comprising pump means; at least two fluid motors; a directional control valve having inlet, motor, and return ports respectively in fluid communication with said pump means, said fluid motors, and a tank; valve members movable in said directional control valve to control actuation of the respective motors and to define variable area orifices in the flow path of pressure fluid to the respective motors of sizes according to the extent of movement of the respective valve members; sensing means responsive to the pressure drops across said variable area orifices operative in conjunction with said pump means to maintain predetermined pressure drops across said orifices thus to actuate said fluid motors at desired speeds according to the sizes of said variable area orifices; check valves downstream of the respective orifices to render said sensing means responsive to the flow demand set by the valve member associated with the fluid motor of higher load pressure in the event of simultaneous actuation of said valve members; and pressure compensating members associated with the respective valve members; each pressure compensating member, when associated with the fluid motor of lower load pressure, sensing the flow demand of the variable area orifice set by the associated valve member and being moved to provide an additional restriction in one of the supply and return paths of fluid in said directional control valve thus to maintain the flow demand set by the variable area orifice of the valve member associated with the fluid motor of lower load pressure.
 2. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve downstream of the variable area orifice set by its associated valve member.
 3. The system of claim 1 wherein one of said pressure compensating members, when moved as aforesaid, provides such additional restriction downstream of the variable area orifice set by its associated valve member.
 4. The system of claim 1 wherein one of said valve members is of three way type defining another variable area orifice in the return path of flow from its associated single acting fluid motor; the associated pressure compensating member sensing the pressure drop across said another variable area orifice and being moved by increase of the latter above a predetermined value to provide additional restriction in the return flow path thus to maintain predetermined return flow as set by said another variable area orifice.
 5. The system of claim 1 wherein one of said pressure compensating members is a spring biased spool-like member axially movable in a bore in said directional control valve and having a first land constituting a load check valve downstream of the variable area orifice set by its associated valve member, and having a second land provided with metering slots defining such additional restriction downstream of the variable area orifice set by its associated valve member.
 6. The system of claim 1 wherein one of said pressure compensating members constitute a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths to and from the associated fluid motor.
 7. The system of claim 6 wherein one of said pressure compensating members, when moved as aforesaid, provides such additional restriction in tHe return flow path from its associated fluid motor.
 8. The system of claim 1 wherein said directional control valve has a load check valve downstream of one of said pressure compensating members.
 9. The system of claim 1 wherein one of said pressure compensating members is a spring biased spool-like member axially movable in a bore in said directioanl control valve and having a first land constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths acting on opposite ends of said spool-like member, and having a second land provided with metering slots defining such additional restriction in said return path, the ends of said spool-like member then being subjected to fluid pressure upstream and downstream of the variable area orifice of its associated valve member.
 10. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve upstream of the variable area orifice set by its associated valve member.
 11. The system of claim 1 wherein one of said pressure compensating members is a spring biased spool-like member which is axially movable in a bore in said directional control valve and which when moved as aforesaid, provides such additional restriction upstream of the variable area orifice of its associated valve member.
 12. The system of claim 11 wherein said one pressure compensating member, when moved as aforesaid, has its opposite ends respectively exposed to pressures upstream and downstream of said variable area orifice.
 13. The system of claim 12 wherein said directional control valve has a spring biased pilot relief valve member therein which is exposed to downstream pressure acting on one end of said spool-like member and which is opened when such downstream pressure exceeds a predetermined value whereby upstream pressure acting on the other end of said spool-like member moves the latter to restrict flow through said additional restriction to the variable area orifice of its associated valve member.
 14. The system of claim 1 wherein said directional control valve has a pilot operated relief valve comprising a spring biased pilot relief member which is exposed to fluid pressure downstream of one variable area orifice and upstream of its associated check valve and which is opened upon such fluid pressure exceeding a predetermined value, and a spring biased main valve member which provides a flow path to said sensing means via said variable area orifices and check valves and which is fluid pressure actuated to restrict said flow path when said pilot relief valve member is opened.
 15. The system of claim 14 wherein said main valve member is axially reciprocable in a bore in said directional control valve and has one end exposed to such fluid pressure and the other end exposed to such fluid pressure via orifice means; the opening of said pilot relief valve member effecting reduction of fluid pressure acting on said other end relative to fluid pressure acting on said one end whereby said main valve member is moved to restrict said flow path as aforesaid.
 16. The system of claim 15 wherein said main valve member is a spool-like member having a groove providing said flow path and an adjacent land to restrict said flow path when said main valve member is moved by predominant fluid pressure acting on said one end.
 17. The system of claim 1 wherein said sensing means comprises an unloading valve having a spring biased unloading valve member movable in a bore in said directional control valve; said unloading valve member having its opposite ends respectively exposed to fluid pressure upstream of said variable area orifices and downstream of said check valves and being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said pump means to said return port.
 18. The system of claim 17 wherein said directional control valve has orifice means communicating said downstream pressure with said return port to retain said downstream pressure at low value when said valve members are in inactive position closing said variable area orifices; said orifice means being saturated upon actuation of either or both of said valve members to establish said variable area orifice or orifices for buildup of downstream pressure for control of said unloading valve member.
 19. The system of claim 18 wherein said orifice means comprises a passage in said unloading valve member.
 20. The system of claim 17 wherein said unloading valve member is a spool-like member having a groove and metering slots in the adjacent land for metering such excess flow.
 21. The system of claim 1 wherein said pump means comprises a variable displacement pump; and wherein said sensing means comprises a pump output adjustment means responding to the pressure drop across said variable area orifices to adjust the output of said pump according to the flow demands set by said valve members.
 22. The system of claim 21 wherein said pump output adjustment means comprises a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifices and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.
 23. The system of claim 22 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage in said directional control valve.
 24. The system of claim 22 wherein said upstream and downstream pressures are derived from respective passages in said directional control valve.
 25. The system of claim 22 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.
 26. The system of claim 22 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.
 27. The system of claim 22 wherein said auxiliary controller at pressure differentials less than such predetermined value is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction.
 28. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve downstream of the variable area orifice set by its associated valve member, and provides such additional restriction downstream of the variable area orifice set by its associated valve member; and wherein the other of said pressure compensating members constitutes a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths to and from the associated fluid motor, and provides such additional restriction in the return flow path from its associated fluid motor.
 29. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve in series with the variable area orifice set by its associated valve member, and provides such additional restriction in series with the variable area orifice of its associated valve member.
 30. The system of claim 29 wherein the other of said pressure compensating members provides such additional restrictiOn in the return flow path from its associated fluid motor.
 31. The system of claim 1 wherein one of said pressure compensating members constitutes a load check valve downstream of the variable area orifice set by its associated valve member; and wherein another one of said pressure compensating members constitutes a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths to and from the associated fluid motor.
 32. The system of claim 1 wherein one of said pressure compensating members, when moved as aforesaid, provides such additional restriction downstream of the variable area orifice set by its associated valve member; and wherein another one of said pressure compensating members, when moved as aforesaid, provides such additional restriction in the return flow path from its associated fluid motor.
 33. The system of claim 1 wherein one of said valve members is of three way type defining another variable area orifice in the return path of flow from its associated single acting fluid motor; the associated pressure compensating member sensing the pressure drop across said another variable area orifice and being moved by increase of the latter above a predetermined value to provide additional restriction in the return flow path thus to maintain predetermined return flow as set by said another variable area orifice; and wherein said directional control valve has a load check valve downstream of another one of said pressure compensating members.
 34. The system of claim 1 wherein one of said pressure compensating members is a spring biased spool-like member axially movable in a bore in said directional control valve and having a first land constituting a load check valve downstream of the variable area orifice set by its associated valve member, and having a second land provided with metering slots defining such additional restriction downstream of the variable area orifice set by its associated valve member; and wherein another one of said pressure compensating members is a spring biased spool-like member axially movable in a bore in said directional control valve and having a first land constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths acting on opposite ends of said spool-like member, and having a second land provided with metering slots defining such additional restriction in said return path, the ends of said spool-like member then being subjected to fluid pressure upstream and downstream of the variable area orifice of its associated valve member.
 35. The system of claim 31 wherein yet another one of said pressure compensating members constitutes a load check valve upstream of the variable area orifice set by its associated valve member.
 36. The system of claim 34 wherein yet another one of said pressure compensating members is a spring biased spool-like member which is axially movable in a bore in said directional control valve and which when moved as aforesaid, provides such additional restriction upstream of the variable area orifice of its associated valve member.
 37. The system of claim 36 wherein said yet another one pressure compensating member, when moved as aforesaid, has its opposite ends respectively exposed to pressures upstream and downstream of said variable area orifice.
 38. The system of claim 37 wherein said directional control valve has a spring biased pilot relief valve member therein which is exposed to downstream pressure acting on one end of said spool-like member of said yet another pressure compensating member and which is opened when such downstream pressure exceeds a predetermined value whereby upstream pressure acting on the other end of said spool-like member moves the latter to restrict flow through said additional restriction to the variable area orifice of its associated valve member.
 39. The system of claim 31 wherein said sensing means comprises an unloading valve having a spring biased unloading valvE member movable in a bore in said directional control valve; said unloading valve member having its opposite ends respectively exposed to fluid pressure upstream of said variable area orifices and downstream of said check valves and being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said pump means to said return port.
 40. The system of claim 39 wherein said directional control valve has orifice means communicating said downstream pressure with said return port to retain said downstream pressure at low value when said valve members are in inactive position closing said variable area orifices; said orifice means being saturated upon actuation of either or both of said valve members to establish said variable area orifice or orifices for buildup of downstream pressure for control of said unloading valve member.
 41. The system of claim 40 wherein said orifice means comprises a passage in said unloading valve member.
 42. The system of claim 39 wherein said unloading valve member is a spool-like member having a groove and metering slots in the adjacent land for metering such excess flow.
 43. The system of claim 31 wherein said pump means comprises a variable displacement pump; and wherein said sensing means comprises a pump output adjustment means responding to the pressure drop across said variable area orifices to adjust the output of said pump according to the flow demands set by said valve members.
 44. The system of claim 43 wherein said pump output adjustment means comprises a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifices and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.
 45. The system of claim 44 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage in said directional control valve.
 46. The system of claim 44 wherein said upstream and downstream pressures are derived from respective passages in said directional control valve.
 47. The system of claim 44 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.
 48. The system of claim 44 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.
 49. The system of claim 44 wherein said auxiliary controller at pressure differentials less than such predetermined value is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction.
 50. The system of claim 35 wherein said sensing means comprises an unloading valve having a spring biased unloading valve member movable in a bore in said directional control valve; said unloading valve member having its opposite ends respectively exposed to fluid pressure upstream of said variable area orifices and downstream of said check valves and being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said pump means to said return pOrt.
 51. The system of claim 50 wherein said directional control valve has orifice means communicating said downstream pressure with said return port to retain said downstream pressure at low value when said valve members are in inactive position closing said variable area orifices; said orifice means being saturated upon actuation of either or both of said valve members to establish said variable area orifice or orifices for buildup of downstream pressure for control of said unloading valve member.
 52. The system of claim 51 wherein said orifice means comprises a passage in said unloading valve member.
 53. The system of claim 50 wherein said unloading valve member is a spool-like member having a groove and metering slots in the adjacent land for metering such excess flow.
 54. The system of claim 35 wherein said pump means comprises a variable displacement pump; and wherein said sensing means comprises a pump output adjustment means responding to the pressure drop across said variable area orifices to adjust the output of said pump according to the flow demands set by said valve members.
 55. The system of claim 54 wherein said pump output adjustment means comprises a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifices and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.
 56. The system of claim 55 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage in said directional control valve.
 57. The system of claim 55 wherein said upstream and downstream pressures are derived from respective passages in said directional control valve.
 58. The system of claim 55 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.
 59. The system of claim 55 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.
 60. The system of claim 55 wherein said auxiliary controller at pressure differentials less than such predetermined value is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction.
 61. The system of claim 31 wherein said directional control valve has a pilot operated relief valve comprising a spring biased pilot relief member which is exposed to fluid pressure downstream of one variable area orifice and upstream of its associated check valve and which is opened upon such fluid pressure exceeding a predetermined value, and a spring biased main valve member which provides a flow path to said sensing means via said variable area orifices and check valves and which is fluid pressure actuated to restrict said flow path when said pilot relief valve member is opened.
 62. The system of claim 61 wherein said main valve member is axially reciprocable in a bore in said directional control valve and has one end exposed to such fluid pressure and the other end exposed to such fluid pressure via orifice means; the opening of said pilot relief valve member effecting reDuction of fluid pressure acting on said other end relative to fluid pressure acting on said one end whereby said main valve member is moved to restrict said flow path as aforesaid.
 63. The system of claim 62 wherein said main valve member is a spool-like member having a groove providing said flow path and an adjacent land to restrict said flow path when said main valve member is moved by predominant fluid pressure acting on said one end.
 64. The system of claim 35 wherein said directional control valve has a pilot operated relief valve comprising a spring biased pilot relief member which is exposed to fluid pressure downstream of one variable area orifice and upstream of its associated check valve and which is opened upon such fluid pressure exceeding a predetermined value, and a spring biased main valve member which provides a flow path to said sensing means via said variable area orifices and check valves and which is fluid pressure actuated to restrict said flow path when said pilot relief valve member is opened.
 65. The system of claim 64 wherein said main valve member is axially reciprocable in a bore in said directional control valve and has one end exposed to such fluid pressure and the other end exposed to such fluid pressure via orifice means; the opening of said pilot relief valve member effecting reduction of fluid pressure acting on said other end relative to fluid pressure acting on said one end whereby said main valve member is moved to restrict said flow path as aforesaid.
 66. The system of claim 65 wherein said main valve member is a spool-like member having a groove providing said flow path and an adjacent land to restrict said flow path when said main valve member is moved by predominant fluid pressure acting on said one end.
 67. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve downstream of said variable area orifice; the movement of said compensating member providing such additional restriction downstream of said variable area orifice.
 68. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve downstream of said variable area orifice; said valve member being of the three way type defining another variable area orifice in the return path of flow between said motor and return ports; said compensating member sensing the pressure drop across said another variable area orifice and being moved by increase of the latter above a predetermined value to provide additional restriction in the return flow path thus to maintain predetermined return flow as set by said another variable area orifice.
 69. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve downstream of said variable area orifice; said compensating member having a first land constituting said load check valve and a second land provided with metering slots defining such additional restriction downstream of the variable area orifice set by its associated valve member.
 70. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid restriction in the return path of fluid flow to maintain the flow demand set by said variable area orifice; said compensating member constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths of fluid flow to and from a double acting fluid motor adapted to be connected to said motor ports; said housing having at least one load check valve downstream of said compensating member.
 71. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively, a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid restriction in the return path of fluid flow to maintain the flow demand set by said variable area orifice; said compensating member constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths of fluid flow to and from a double acting fluid motor adapted to be connected to said motor ports; said housing having load check valves in passages leading to said motor ports downstream of said compensating member; said housing also having bypass passages to bypass the respective load check valves for return fluid flow from the respective motor porst to said return port via said valve member.
 72. A pressure compensated directional control valve for an integrated Pressure compensated load sensing system and the like comprising a housing having inlet, motor, and return ports for connection with a fluid pressure source, a fluid motor, and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid restriction in the return path of fluid flow to maintain the flow demand set by said variable area orifice; said compensating member constituting a counterbalance valve which is opened by predetermined pressure differential in the supply and return paths of fluid flow to and from a double acting fluid motor adapted to be connected to said motor ports; said compensating member having a first land constituting said counter-balance valve which is opened by predetermined pressure differential in the supply and return paths acting on opposite ends of said compensating member, and having a second land provided with metering slots defining such additional restriction in said return path, the ends of said compensating member then being subject to fluid pressure upstream and downstream of said variable area orifice.
 73. A pressure compensated directional control valve for an integrated pressure compensated load sensing system and the like comprising a housing having inlet, motorm and return ports for connection with a fluid pressure source, a fluid motor and a tank respectively; a spool valve member movable in a bore in said housing to control actuation of such fluid motor and to define a variable area orifice in the flow path of pressure fluid between said inlet and motor ports of size according to the extent of movement of said valve member; a spring biased spool-like pressure compensating member movable in another bore in said housing and having opposite end portions exposed to fluid pressure upstream and downstream of said variable area orifice to provide additional restriction in the supply path of pressure fluid to maintain the flow demand set by said variable area orifice; said compensating member constituting a load check valve upstream of said variable area orifice; said compensating member providing such additional restriction upstream of said variable area orifice; and a spring biased pilot relief valve member in said housing exposed to downstream pressure acting on one end of said compensating member; said pilot relief valve member being opened when such downstream pressure exceeds a predetermined value whereby upstream pressure acting on the other end of said compensating member moves the latter to restrict flow through said additional restriction to said variable area orifice.
 74. An unloading valve for an integrated pressure compensated load sensing system and the like comprising a housing having a supply passage for flow of pressure fluid from a pump to a fluid motor via a variable area orifice in a directional control valve and a return passage leading to a tank; a spring biased spool-like unloading valve member movable in a bore in said housing and having its opposite ends respectively exposed to fluid pressure upstream and downstream of such variable area orifice; said unloading valve member being moved by the pressure differential acting on said ends exceeding a predetermined value to bypass excess flow from said supply passage to said return passage; and orifice means in said unloading valve communicating said downstream pressure with said return passage to retain said downstream pressure at low value when said variable area orifice is closed; said orifice means being saturated upon establishment of said variable area orifice for buildup of downstream pressure for control of said unloading valve member.
 75. The unloading valve of claim 74 wherein said Orifice means comprises a passage in said unloading valve member.
 76. Output adjustment means for the variable displacement pump of an integrated pressure compensated load sensing system and the like, said output adjustment means responding to the pressure drop across a variable area orifice to adjust the output of said pump according to the flow demand set by said variable area orifice; said pump output adjustment means comprising a movable displacement varying member; a spring and fluid pressure actuated control piston effective to move said displacement varying member in displacement increasing direction or to permit the latter to move in displacement decreasing direction; a main spring biased controller actuated by pump delivery pressure to apply force through spring means on said control piston in displacement increasing direction and to conduct upstream pressure to act on said control piston; an auxiliary spring biased controller exposed to fluid pressure upstream and downstream of said variable area orifice and operative upon the differential of said upstream and downstream pressures exceeding a predetermined value, to open a bleed orifice from said control piston to the intake side of said pump thus to discontinue movement of said displacement member in displacement increasing direction.
 77. The output adjustment means of claim 76 wherein said upstream pressure is derived from the delivery side of said pump, and said downstream pressure is derived from a passage communicating with the dowstream side of said variable area orifice.
 78. The output adjustment means of claim 76 wherein said upstream and downstream pressures are derived from respective passages communicating with the upstream and downstream sides of said variable area orifice.
 79. The output adjustment means of claim 76 wherein another spring means acts on said control piston at zero displacement position of said displacement varying member to provide for movement of said control piston in displacement increasing direction when said pump is started.
 80. The output adjustment means of claim 76 wherein said main controller, upon predetermined movement in displacement increasing direction opens another bleed orifice from said control piston to the intake side of said pump.
 81. The output adjustment means of claim 76 wherein said auxiliary controller, at pressure differentials less than such predetermined value, is effective to close said bleed orifice for continued movement of said control piston in displacement increasing direction. 